/*
    * Copyright 2022 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (the "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at:
    *
    *   https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  package io.netty.handler.ssl;
  
  import io.netty.util.CharsetUtil;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
  import org.bouncycastle.openssl.PEMDecryptorProvider;
  import org.bouncycastle.openssl.PEMEncryptedKeyPair;
  import org.bouncycastle.openssl.PEMKeyPair;
  import org.bouncycastle.openssl.PEMParser;
  import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
  import org.bouncycastle.openssl.jcajce.JceOpenSSLPKCS8DecryptorProviderBuilder;
  import org.bouncycastle.openssl.jcajce.JcePEMDecryptorProviderBuilder;
  import org.bouncycastle.operator.InputDecryptorProvider;
  import org.bouncycastle.operator.OperatorCreationException;
  import org.bouncycastle.pkcs.PKCS8EncryptedPrivateKeyInfo;
  import org.bouncycastle.pkcs.PKCSException;
  
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.FileReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.security.AccessController;
  import java.security.PrivateKey;
  import java.security.PrivilegedAction;
  import java.security.Provider;
  
  final class BouncyCastlePemReader {
      private static final String BC_PROVIDER = "org.bouncycastle.jce.provider.BouncyCastleProvider";
      private static final String BC_PEMPARSER = "org.bouncycastle.openssl.PEMParser";
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(BouncyCastlePemReader.class);
  
      private static volatile Throwable unavailabilityCause;
      private static volatile Provider bcProvider;
      private static volatile boolean attemptedLoading;
  
      public static boolean hasAttemptedLoading() {
          return attemptedLoading;
      }
  
      public static boolean isAvailable() {
          if (!hasAttemptedLoading()) {
              tryLoading();
          }
          return unavailabilityCause == null;
      }
  
      /**
       * @return the cause if unavailable. {@code null} if available.
       */
      public static Throwable unavailabilityCause() {
          return unavailabilityCause;
      }
  
      private static void tryLoading() {
          AccessController.doPrivileged(new PrivilegedAction<Void>() {
              @Override
              public Void run() {
                  try {
                      ClassLoader classLoader = getClass().getClassLoader();
                      // Check for bcprov-jdk18on:
                      Class<Provider> bcProviderClass =
                              (Class<Provider>) Class.forName(BC_PROVIDER, true, classLoader);
                      // Check for bcpkix-jdk18on:
                      Class.forName(BC_PEMPARSER, true, classLoader);
                      bcProvider = bcProviderClass.getConstructor().newInstance();
                      logger.debug("Bouncy Castle provider available");
                      attemptedLoading = true;
                  } catch (Throwable e) {
                      logger.debug("Cannot load Bouncy Castle provider", e);
                      unavailabilityCause = e;
                      attemptedLoading = true;
                  }
                  return null;
              }
          });
      }
  
      /**
       * Generates a new {@link PrivateKey}.
       *
       * @param keyInputStream an input stream for a PKCS#1 or PKCS#8 private key in PEM format.
      * @param keyPassword the password of the {@code keyFile}.
      *                    {@code null} if it's not password-protected.
      * @return generated {@link PrivateKey}.
      */
     public static PrivateKey getPrivateKey(InputStream keyInputStream, String keyPassword) {
         if (!isAvailable()) {
             if (logger.isDebugEnabled()) {
                 logger.debug("Bouncy castle provider is unavailable.", unavailabilityCause());
             }
             return null;
         }
         try {
             PEMParser parser = newParser(keyInputStream);
             return getPrivateKey(parser, keyPassword);
         } catch (Exception e) {
             logger.debug("Unable to extract private key", e);
             return null;
         }
     }
 
     /**
      * Generates a new {@link PrivateKey}.
      *
      * @param keyFile a PKCS#1 or PKCS#8 private key file in PEM format.
      * @param keyPassword the password of the {@code keyFile}.
      *                    {@code null} if it's not password-protected.
      * @return generated {@link PrivateKey}.
      */
     public static PrivateKey getPrivateKey(File keyFile, String keyPassword) {
         if (!isAvailable()) {
             if (logger.isDebugEnabled()) {
                 logger.debug("Bouncy castle provider is unavailable.", unavailabilityCause());
             }
             return null;
         }
         try {
             PEMParser parser = newParser(keyFile);
             return getPrivateKey(parser, keyPassword);
         } catch (Exception e) {
             logger.debug("Unable to extract private key", e);
             return null;
         }
     }
 
     private static JcaPEMKeyConverter newConverter() {
         return new JcaPEMKeyConverter().setProvider(bcProvider);
     }
 
     private static PrivateKey getPrivateKey(PEMParser pemParser, String keyPassword) throws IOException,
             PKCSException, OperatorCreationException {
         try {
             JcaPEMKeyConverter converter = newConverter();
             PrivateKey pk = null;
 
             Object object = pemParser.readObject();
             while (object != null && pk == null) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("Parsed PEM object of type {} and assume " +
                                  "key is {}encrypted", object.getClass().getName(), keyPassword == null? "not " : "");
                 }
 
                 if (keyPassword == null) {
                     // assume private key is not encrypted
                     if (object instanceof PrivateKeyInfo) {
                         pk = converter.getPrivateKey((PrivateKeyInfo) object);
                     } else if (object instanceof PEMKeyPair) {
                         pk = converter.getKeyPair((PEMKeyPair) object).getPrivate();
                     } else {
                         logger.debug("Unable to handle PEM object of type {} as a non encrypted key",
                                      object.getClass());
                     }
                 } else {
                     // assume private key is encrypted
                     if (object instanceof PEMEncryptedKeyPair) {
                         PEMDecryptorProvider decProv = new JcePEMDecryptorProviderBuilder()
                                 .setProvider(bcProvider)
                                 .build(keyPassword.toCharArray());
                         pk = converter.getKeyPair(((PEMEncryptedKeyPair) object).decryptKeyPair(decProv)).getPrivate();
                     } else if (object instanceof PKCS8EncryptedPrivateKeyInfo) {
                         InputDecryptorProvider pkcs8InputDecryptorProvider =
                                 new JceOpenSSLPKCS8DecryptorProviderBuilder()
                                         .setProvider(bcProvider)
                                         .build(keyPassword.toCharArray());
                         pk = converter.getPrivateKey(((PKCS8EncryptedPrivateKeyInfo) object)
                                                              .decryptPrivateKeyInfo(pkcs8InputDecryptorProvider));
                     } else {
                         logger.debug("Unable to handle PEM object of type {} as a encrypted key", object.getClass());
                     }
                 }
 
                 // Try reading next entry in the pem file if private key is not yet found
                 if (pk == null) {
                     object = pemParser.readObject();
                 }
             }
 
             if (pk == null) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("No key found");
                 }
             }
 
             return pk;
         } finally {
             if (pemParser != null) {
                 try {
                     pemParser.close();
                 } catch (Exception exception) {
                     logger.debug("Failed closing pem parser", exception);
                 }
             }
         }
     }
 
     private static PEMParser newParser(File keyFile) throws FileNotFoundException {
         return new PEMParser(new FileReader(keyFile));
     }
 
     private static PEMParser newParser(InputStream keyInputStream) {
         return new PEMParser(new InputStreamReader(keyInputStream, CharsetUtil.US_ASCII));
     }
 
     private BouncyCastlePemReader() { }
 }